Receiving circuit



y 31, 1932- H. D. CURRIER 1,860,997

RECEIVING CIRCUIT Filed April 22; 1925 2 Sheets-Shet 1 IIIIII y 31,1932- H. D. CURRIER 1,860,997

RECEIVING CIRCUIT Filed April 22, 1925 2 Sheets-Sheet 2 Patented May 31,1932 2 UNITED STATES PATIENT OFFICE HIRAM D. GURRIER, OF CHICAGO,ILLINOIS, ASSIG-NOR TO KELLOGG- SWITCHBOARD AND SUPPLY CO1\IPANY,'OFCHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS RECEIVING orneurr Myinvention relates to wireless telegraphy and telephony and resides innovel circuit arrangements for such systems, and in the accompanyingdrawings my invention is shown as employed for thereception of radiosignals. My invention however is not limited to receptive purposes only,and its objects are to provide a novel and improved organization of theelements comprising such a system, and which provides an arrangementaffording sharpness of tuning, ease of control, power, and'clearness inrespectto the signals received.

Figs. 1 and 2 of the drawings show receiving arrangements involvingradio frequency amplification, detection and audio frequencyamplification. In systems of the prior art which made use of tuned radiofrequency amplification it has been customary-to provide at least atuning unit per stage of radio frequency amplification. This arrangementhas made the tuning somewhat complicated, especially where severalstages of radio amplification was provided. It is a feature of myinvention to reduce the number of controls heretofore used and to tunemore than one stage of amplification with one control device.

Referring particularly to the drawings:

Fig.1 shows a system in which the secondaries of a plurality oftransformers are tuned in series, and r e Fig. 2 shows a system in whichthe secondaries of a plurality of transformers are tuned in multiple.

Referring particularly to Fig. 1 of the drawings which shows thepreferred embodiment of my invention, 2, 3,4 and 5 represent radiofrequency transformers, which may be of the air core type, each onecomprising a primary winding and a secondary winding. The audiontubes'6, 7 8, 9, 10 and 11 are of the three electrode type, eachincludinga filament, a grid and a plate. Tubes 6, 7, and8 are used asradio frequency amplifiers, tube 9 as a detector, and audion tubes 10and 11 as audio frequency amplifiers. The

audio frequency transformers l2 and 13 are provided with iron-cores, andthe primary is grounded at 20, is the usual primary batteryforfurnishing heating current to the filaments of the audion tubes, andbatteries 21, 22 and 23 are the usual B battery for furnishing currentto the plates of the audion tubes. The plate circuit of 'audion tube 11includes a pair of receivers 24 which may be replaced by a loud speakerof the type now in use. Rheostats R, R and R control the supply ofcurrent to the filaments of tubes 6,

7 and 8, respectively, rheostat R to the fila- I ment of the detectortube 9, and rheostat R controls the supply of heating current to thefilaments of tubes 10 and 11. At 25 I represent the ordinary antenna orcollector device for receiving the incoming oscillations.

Bridged across battery 19 is a resistance 28 which has its central pointtapped and connected in the grid return circuits of audion tubes 6, 7 8and 9. Bridged from this central point of the resistance 28 to ground 20is a by-pass condenser 29.

Having given a brief description' of the apparatus involved in mysystem, I will now briefly refer to the functioning of the same.

The incoming oscillations are picked up by the antenna 25 and passthrough the primary 26 of the transformer 2 toground 20. The incomingoscillations or signals are induced in the secondary 31 of thetransformer 2 and are operative upon the grid of tube 6 to repeat thesignal through the primary 27 of transformer 3. The signal is theninduced into the secondary 32 of the transformer 3 andis operative uponthe grid of tube 7 to repeat the saidsignal through the primary 30 oftransformer 4. 'The signal --is induced into the secondary 33 of thetrans former 4 and is operative upon the grid of the audion tube 8 torepeat the signal through the primary 34: of the transformer 5. The

signal in turn is operative upon the grid of the tube 9 through thesecondary of the transformer 5. The tube 9 through its plate circuitrelays the signal through the primary 36 of the audio frequencytransformer 12. The transformer 12 operates to make the signal operativeupon the grid of tube 10 which in turn transmits a signal through theprimary 38 of the audio frequency transformer 13. This signal is inducedinto the secondary 39 of the transformer 13 and is operative upon thegrid of tube 11. Tube 11 operates to reproduce the signal in the platecircuit thereof through the receivers 24 to the posi tive pole of Bbattery 23. V

The method of operating the set is to adjust the rheostats so that theright amount of current is supplied to the filaments of the tubes and tothen operate variable condensers 15 and 16 until the secondaries 3132and 3335 of the transformers 2, 3, 4 and 5 are in resonance with theincoming signal so that the same may be amplified by the apparatus tothe exclusion of the undesired signals. The condenser 15 tunes thesecondaries 31 and 32 of transformers 2 and 3, and permits the desiredoscillations to be induced from the primary 26 of transformer 2 into thesecondary 31 thereof and for the repeated impulse to be induced from theprimary 27 of the transformer 3 into the secondary 32 thereof. Likewise,the condenser 16 tunes the secondaries 33 and 35 of transformers 4 and 5so that the desired signal may pass through these transformers and beoperative upon the grids of the tubes to cause the signal to beamplified.

This arrangement permits the use of three stages of tuned radiofrequency amplification and a detector stage with the use of only twovariable or adjustable condensers. This simplifies the control a greatdeal, as one condenser 15 controls two stages of amplification andpermits only the desired signal to pass while the condenser 16 controlstwo stages of amplification and permits the desired signal to beoperative upon the grid of the detector tube.

While I have not gone into the theory of operation of the circuits it isthought that the foregoing description is sufficient to permit oneskilled in the art to practice the invention.

Referring to Figure 2 the apparatus in this figure is quite similar tothat in Figure 1 but here I provide a different method of tuning. Thevariable condenser 40 is in multiple with the secondary windings and .81of transformers 41 and 42 of the first two stages of radio frequencyamplification. Variable condenser 43 is in multiple with the secondarywindings 82 and 83 of transformers 44 and 45 and variable condenser 46is in multiple with the secondaries 84 and of transformers 47 and 48. Inthis figure I tune the secondaries of the transformers in multipleinstead of in series as in Figure 1. Figure 2 discloses five stages ofradio frequency amplification and a detector stage all controlled bythree variable condensers. The audio frequency transformers 50 and 51are of the usual iron core type and at 52 I have shown a pair ofreceivers in the plate circuit of the last audion tube 53. The primarybattery 54 and the secondary battery 55, 56 and 57 are for the purposesdiscussed in connection with Figure 1. The resistance 58 and condenser59 are the same as used in connection with the apparatus of Figure 1. Ialso provide rheostats 60 to 67 inclusive for controlling the heatingcurrent to the filaments of the audion tubes. The plate of tube 7 0, itwill be noted is coupled through the transformer 42 to the grids oftubes 7 0 and 71. The plates of tubes 7 2 and 74 likewise are coupledrespectively through transformers 45 and 48 to the grids of tubes 7 2and 7 3 and the grids of tubes 74 and 75.

This feature appears to give marked results in the reception of signals.On account of the very high frequency of the oscillatory currentsinvolved in systems of this character and their tenuity together with asensitively balanced effect that exists when such systems are operatedit is as is well known quite diflicult to determine the precise actionsand reactions involved, but the foregoing description is sufiicient toenable any one skilled in the art to readily practice the invention.

From the foregoing it will be seen that in both Figures 1 and 2 Iprovide one variable condenser or tuning device for tuning two stages ofamplification and that this method of tuning reduces the number ofcondensers normally used to operate a pre-determined number of stages ofradio frequency amplification.

While I have shown two specific arrangements of my invention, I do notdesire to be limited to the exact manner shown and described, but aim tocover all that which comes within the spirit and scope of the appendedclaims.

Having described my invention what I claim as new and desire to secureby United States Letters Patent is:

1. A radio receiving system of the character described including aplurality of transformers connected in successive stages of the radioreceiving circuit and each having primary and secondary windings, and asingle variable tuning device connected directly to similar points of aplurality of said secondary windings for tuning the same.

2. A multi-stage radio circuit of the character described including aplurality of transformers connected in successive stages of the radiocircuit operating in connection with audion tubes, said transformershaving primary and secondary windings, and a single variable condenserdirectly connected between similar points on the said secondary windingsfor tuning the same.

8. A radio receiving arrangement includ ing a pair of transformers insuccessive stages of the radio receiving circuit and each having primaryand secondary windings, audion tubes associated therewith, and a singlevariable condenser connected between similar points on a winding of eachof said transformers for directly tuning said winding of each of saidtransformers.

4. A receiving circuit of the character described including a pair oftransformers, each transformer being in a different stage of thereceiving circuit and each having primary and secondary windings, a pairof audion tubes, one terminal of each of said secondary windings beingconnected to an element of said tubes, and a single variable tuningdevice serially connected to said secondary windings for controlling thesame, said tuning device being connected between similar points on saidsecondary windings.

5. A'multi-stage receiving arrangement of the character describedincluding transformers, a transformer for each stage and eachtransformer having primary and secondary windings, a pair of audiontubes associated with said transformers, and a single adjustv ablecondenser for simultaneously tuning said secondary windings in series,said condenser being directly connected between similar points on therespective secondaries of said transformers.

6. A cascade receiving arrangement of the character described, atransformer for each stage of said receiving circuit and eachtransformer having primary and secondary windings, a plurality of audiontubes associated and connected to said transformers, and a singlevariable tuning element serially connected'with said secondary windingsof said tranformer and connected between similar points on therespective secondary windings of said transformers for tuning the same.

7 A cascade receiving arrangement of the character described, a pair oftransformers one in each stage of the receiving circuit and havingprimary and secondary windings, audion tubes associated and connectedwith said transformers, one terminal of the secondary of each of saidtransformers being connected together, the other terminal of each ofsaid secondaries being connected to grid elements of said tubes, and asingle variable tuning device connected between said grid elements fortuning purposes.

8. A cascade radio frequency amplifier coupled by transformers, onetransformer for each stage, and common tuning means comprising a singlecondenser directly connected between similar points on the respectivesecondaries of said transformers.

9. A system of the character described including a plurality of stagesof tuned radio I said transformers, means including a device having asingle movable and a single stationary element for tuning a winding ofthe transformer of one of said stages and connections whereby thetransformer of another of said stages is automatically tuned to the samefrequency when the said winding of said first transformer is tuned.

10. A tuning system of the character described including a plurality ofstages and tuned amplification, a transformer and an audion tube foreach of said stages, circuits connecting elements of said tubes towindings of said transformers, tuning devices having single movableelements and single stationary elements connected to windings of saidtransformers for tuningthe transformers of some of the stages ofamplification, and other circuit connections so arranged that when saidfirst transformers are tuned the other transformers of the other of saidstages of amplification are simultaneously tuned.

11. In radio signaling apparatus, a plurality of stages, each includinga thermionic device, means for simultaneously tuning said stages to adetermined signal, said means comprising a fixed reactance connected ineach stage, and a variable reactance common to said plurality of stages.

Signed by me at Chicago, in the county of Cook, and State of Illinois,this 20th day of April, 1925.

HIRAM D. CURRIER.

